Polarization independence of laser-induced nucleation in supersaturated aqueous urea solutions

Liu, Yao and Ward, Martin R. and Alexander, Andrew J. (2017) Polarization independence of laser-induced nucleation in supersaturated aqueous urea solutions. Physical Chemistry Chemical Physics, 19 (5). pp. 3464-3467. ISSN 1463-9076

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    Abstract

    In a seminal report on laser-induced nucleation in aqueous supersaturated solutions (Phys. Rev. Lett., 1996, 77, 3475) it was noted that needle-shaped crystals of urea were aligned with the direction of the electric field of the linearly polarized laser pulse. The results gave rise to a new mechanism for control of crystal nucleation involving alignment of solute molecules (optical Kerr effect) now commonly known as non-photochemical laser-induced nucleation (NPLIN). Recent theoretical and experimental work has cast doubts on the optical Kerr effect mechanism. In the present letter we present results from digital imaging of urea-crystal growth immediately following laser-induced nucleation. Analysis of the data shows no statistically significant correlation between crystal angle and direction of linear polarization. The results overturn a long-held result that has shaped theoretical and experimental studies of NPLIN.